Hedge-fund manager Paul Singer took a stand after Argentina defaulted, holding onto his bonds and refusing to swap them in the restructuring the government began in 2005. Jump ahead to 2014. Singer, still fighting for full recovery on the debt, has, with help from U.S. courts, pushed Argentina into a second default as the country maintained its stance against paying him.

These actions have landed Singer on the fourth annual Bloomberg Markets 50 Most Influential list, which appears in the magazine's October special issue.

The people we've selected reach across borders and transcend obstacles. General Electric Co. Chief Executive Officer Jeffrey Immelt has almost completed a $17 billion acquisition of Alstom SA's power-generation business, having dealt personally with the French government to convince it that his bid was superior to a rival German-Japanese offer.

Ana Patricia Botin has turned around the U.K. operations of Banco Santander SA, adding customers and boosting profits, a level of success that could position her to run the parent company, as her father, grandfather and great-grandfather did before her.

To arrive at our 50, we start with a larger group of candidates assembled with the help of Bloomberg News journalists in bureaus across the globe. Rankings and profiles published in Bloomberg Markets throughout the year help guide the selection process, with the magazine's editors narrowing the final list to 10 people in each of five categories: Money Managers, Thinkers, Corporate Power Brokers, Bankers and Policy Makers. We select individuals based on what they're doing now, rather than past achievements, and almost three-fifths of this year's list is made up of people who are appearing for the first time.

Leon Cooperman, 71
Founder
Omega Advisors Inc.
Was in top 20 of the Bloomberg Markets annual ranking of large hedge funds. Grabs the attention of other investors whenever he buys or sells.

Larry Fink, 61
Co-Founder
BlackRock Inc.
Runs the world's biggest money management firm. Has pushed to keep it from being labeled systemically important and subjected to extra regulatory scrutiny, and has succeeded so far.

Carl Icahn, 78
Chairman
Icahn Enterprises LP
Pushed Apple to do more buybacks and Family Dollar Stores Inc. to sell itself, among other efforts. Sees an asset bubble caused by Fed policy.

Helena Morrissey, 48
CEO
Newton Investment Management
Is bringing the 30% Club, which she founded to advocate for more women on corporate boards, to the U.S. Chairs the Investment Management Association in the U.K.

Stephen Schwarzman, 67
Co-founder
Blackstone Group LP
Oversees the largest private-equity firm, where assets under management have reached $279 billion and activities include much more than just buyouts these days.

Timothy Garton Ash, 59
Professor
University of Oxford
Brings historical perspective to the ``Putin Doctrine.'' Warns of the danger inherent in Putin's assertion that Russians outside of Russia deserve his protection.

Jack Bogle, 85
Founder
Vanguard Group Inc.
Is the voice of reason on old topics, such as the foolishness of high fees, and new, as when he defends high-frequency trading as mostly positive.

Lael Brainard, 52
Governor
U.S. Federal Reserve
Praises the increased capital buffers of U.S. banks and the Volcker Rule, opinions backed up by a Washington career that dates back to the Asian financial crisis.

Satyajit Das, 57
Author
``Traders, Guns and Money''
Is gloomy about how global monetary stimulus gets withdrawn without a crash and how China balances its economy. Keeps his sense of humor anyway.

Charmian Gooch, 49
Co-Founder
Global Witness
Is fighting graft in the developing world and pushing for new rules on shell companies, used to hide ownership.

Paul Graham, 49
Partner
Y Combinator
Has provided seed funding through his tech accelerator for some 700 startups now worth more than $30 billion total, including Reddit Inc., Airbnb Inc. and Dropbox Inc.

Charles Grant, 55
Executive Director
Centre for European Reform
Defends the European Union against those who have forgotten why it was created and promotes changes. Says David Cameron isn't helping matters.

Kathy Matsui, 49
Chief Japan Equity Strategist
Goldman Sachs Group Inc.
Coined the term womenomics in 1999 to describe the economic advantages of more women in the workforce. Has now seen those ideas embraced as a feature of Japan's Abenomics.

Jacqueline Novogratz, 53
CEO
Acumen
Through her nonprofit, supplies what she calls patient capital along with management expertise for small companies that provide housing, energy, health care and more in poor nations.

Thomas Piketty, 43
Professor
Paris School of Economics
Became a cause célèbre after his ``Capital in the Twenty-First Century'' was published in English in March, rallying left-leaning economists with new data and ideas on income inequality.

Rinat Akhmetov, 47
Founder
System Capital Management
Is trying to keep his workers from joining pro-Russian forces and maintain his grip on the industrial empire that made him Ukraine's richest man.

Mary Barra, 52
CEO
General Motors Co.
With her reputation at stake, has testified to Congress four times, walking a fine line between defense of the company and promises that it will change.

Warren Buffett, 84
CEO
Berkshire Hathaway Inc.
Says Berkshire shares, above $200,000 for the first time, are too rich for him. Has $55 billion in cash on hand for acquisitions if he wants.

Tim Cook, 53
CEO
Apple Inc.
Has convinced investors that new products and better phones are in the pipeline. Apple shares are back near their all-time high.

Guo Guangchang, 47
Founder
Fosun Group
Seeks to emulate Buffett's Berkshire Hathaway while focusing on the needs of the Chinese consumer.

Jeffrey Immelt, 58
CEO
General Electric Co.
Has kept the $16 billion purchase of Alstom SA's power generation assets on course, even gaining French government approval. Continues to shrink financial services.

Jack Ma, 49
Founder
Alibaba Group Holding Ltd.
Is marketing the largest-ever U.S. initial public offering, positioning Alibaba as a global player -- not just China's biggest e-commerce company.

Elon Musk, 43
Founder
Tesla Motors Inc.
Is a darling of investors, with Tesla's market capitalization rapidly rising toward that of General Motors, which has more than 50 times the sales.

Xavier Niel, 47
Founder
Iliad SA
Is the exception to the rule that France does not produce risk-taking entrepreneurs. Is bidding for T-Mobile US Inc., which so far has rejected the overture.

Igor Sechin, 54
CEO
OAO Rosneft
Runs the world's biggest publicly traded oil company as measured by output and reserves. Is close enough to Putin to merit U.S. sanctions.

Lloyd Blankfein, 59
CEO
Goldman Sachs Group Inc.
Has joked about keeping his job until he dies at his desk. Is committed to Goldman's trading business, hoping to benefit as rivals pull back.

Ana Patricia Botin, 53
CEO
Santander U.K. Plc
Runs the unit setting the pace for earnings growth for parent Banco Santander SA of Spain. Would be the fourth Botin generation to run Santander if she rises to the top job.

James Gorman, 56
CEO
Morgan Stanley
Has brought investors around to his strategy, which relies on retail brokerage for consistent profits. Shares are up 30 percent in 12 months.

Jiang Jianqing, 61
Chairman
Industrial & Commercial Bank of China Ltd.
In charge for 13 years, has transformed a firm that was nearly insolvent into the world's most profitable bank. Is expanding outside of China.

Kenneth Moelis, 56
CEO
Moelis & Co.
Completed the initial share sale of his firm, the first investment bank to go public since 2007. Has ridden an M&A surge to a valuation of nearly $1.9 billion.

John Stumpf, 60
CEO
Wells Fargo & Co.
Oversees the most valuable bank by market capitalization in the world. Has been seven years in the top job, during which time Wells Fargo has outperformed its rivals.

Paul Taubman, 53
Principal
PJT Capital LLC
Even without the heft of Morgan Stanley, which he left in 2013, will get big advisory fees on the pending Comcast Corp. acquisition of Time Warner Cable Inc.

Axel Weber, 57
Chairman
UBS AG
Understands the regulatory trends and is shaping the Swiss giant's business strategy accordingly. Remains an important monetary hawk as a former German central banker.

Preet Bharara, 45
U.S. Attorney
Justice Department
Ran his insider-trading investigation all the way up to Steven Cohen's firm, if not Cohen himself. Is tangling with New York Governor Andrew Cuomo over an anti-corruption commission.

Mario Draghi, 67
President
European Central Bank
Unveiled a package of measures to fight slow growth and avoid deflation. Updated his whatever-it-takes pledge with a simple promise: that he's not finished.

Jason Furman, 44
Chairman
White House Council of Economic Advisers
Has worked for Obama since before he was president and is now his top economic adviser. Says the economy would do better if Congress would boost infrastructure spending.

Idris Jala, 56
CEO of Pemandu
Malaysian Prime Minister's Office
Is making it easier to invest and do business in Malaysia as he shapes economic policy meant to help the country catch up to its more-developed neighbors.

Benjamin Lawsky, 44
Superintendent
New York Department of Financial Services
Has shown how a state regulator can trump bigger agencies, as when he pushed a tougher settlement on France's BNP Paribas SA.

George Osborne, 43
Chancellor of the Exchequer
United Kingdom
Is claiming bragging rights as the U.K. grows faster than the euro zone and the U.S. following the period of austerity his government imposed.

Raghuram Rajan, 51
Governor
Reserve Bank of India
Has stabilized the rupee and put up a more-credible fight against inflation. Wants to change government aid to the poor to cut out corrupt middlemen and politicians.

Xiao Gang, 56
Chairman
China Securities Regulatory Commission
Has pushed banks and companies to set new share offerings at attractive prices to shield retail investors from losses, and China's IPOs have outperformed as a result.

Zhou Xiaochuan, 66
Governor
People's Bank of China
Is the longest-serving central bank chief since the establishment of the People's Republic, in the job since 2002. Is cracking down on shadow banking.